Average human life expectancy has been increasing over the past several decades. One result of this phenomenon is that an increasing number of patients require treatment for diseased vasculature, such as narrowing of the arteries due to plaque accumulation. Treatment of constricted arteries typically involves pre-dilating the vessel using an angioplasty balloon, followed by placing a stent in the vessel to retain the patency of the vessel. Often, pieces of the plaque break free from the vessel wall during the angioplasty procedure and/or stent placement, and pose a risk of blocking smaller downstream vessels, thus presenting a risk of infarction or stroke.
Several prior systems have been developed to capture emboli liberated during an interventional procedure such as angioplasty or stent delivery. Such systems generally seek either to capture the emboli using a filter disposed downstream of the treatment site, or a suction system configured to aspirate emboli-laden blood from the treatment site, or a combination of both.
For example, U.S. Pat. No. 5,549,626 to Miller et al. discloses a mesh-like filter basket that is deployed within the blood vessel to collect emboli liberated from the treatment site. Emboli first are captured in the basket and then aspirated from the vessel.
One disadvantage of the type of system described in Miller et al. is that the basket may become dislodged during the procedure, allowing the emboli to travel past the basket and pass into downstream circulation. Accordingly, it would be desirable to provide apparatus and methods for extracting emboli from a treatment site that do not involve deployment of a filter within the blood vessel.
U.S. Pat. No. 5,833,650 to Imran describes a multiple coaxial catheter system in which occlusion balloons are deployed proximal and distal to a lesion to define a treatment site. An intermediate balloon then may be advanced between the proximal and distal balloons to perform angioplasty, and any resulting emboli are aspirated from the treatment site using a suction pump. The aspirated blood is extracorporeally filtered and returned through a lumen of the innermost catheter to a location downstream of the distal balloon. The system described in Imran poses inherent risks associated with mechanically pumping blood from an occluded segment of vessel, e.g., such as vessel collapse. In addition, the use of multiple coaxial catheters limits the cross-sectional area of the lumen used to return blood to the patient's vasculature, leading to potential hemolysis, and limits the diameter of vessels in which the system practically may be employed.
U.S. Pat. No. 6,540,712 to Parodi et al. describes an alternative approach to embolic protection, in which emboli-laden blood is withdrawn from the treatment site using naturally-occurring pressure differentials. Withdrawn blood is extracorporeally filtered to remove the emboli and then the filtered blood is returned to the body via a connection the patient's venous vasculature. While that system has been proven to be highly effective at removing emboli, the use of a separate incision to place the venous return line has slowed its commercial adoption.
It therefore would be desirable to provide a system that enables blood to be withdrawn from the treatment site to be filtered, but which overcomes the drawbacks of previously known systems, such as the size limitations imposed by the multi-catheter arrangement of the Imran system or the need to provide multiple connections to the patient's circulatory system, as in the system of Parodi et al.
In addition, many rotational atherectomy devices are known in the art for removing plaque from within a vessel. For example, U.S. Pat. No. 5,376,100 to Lefebvre describes a device having a cylindrical member that expands radially when rotated at high speeds. Care must be taken when using the device to ensure that the cutting member does not contact the vessel wall and potential damage the vessel endothelium. U.S. Pat. No. 6,660,014 to Demarais, et al., also describes a rotating device deployed via catheter to the occlusion site, but with similar limitations.
It therefore would be desirable to provide a plaque removal device that reduces the risk posed by previously-known devices. In particular, it would be desirable to provide a plaque removal device that inherently self-centers within a vessel, so as to reduce the risk of damage to the vessel lining. In addition, it would be desirable to provide such a system having a minimum of mechanical complexity.
In view of the drawbacks of previously known methods and apparatus, it would be desirable to provide embolic protection apparatus and methods that allow emboli-laden blood to be removed from the treatment site, extracorporeally filtered, and returned to the patient's vasculature without multiple connections.
It also would be desirable to provide embolic protection apparatus and methods having bi-directional flow capability, while also preventing intermingling of filtered and unfiltered blood.
It further would be desirable to provide a plaque removal system for use with the proposed embolic protection apparatus, wherein the plaque removal system reduces the risk of damage to the vessel lining.